1. Field of the Invention
The present invention relates to a scroll type fluid displacement apparatus, and more particularly, to the sealing mechanism between a pair of the scroll members for the scroll type fluid displacement apparatus.
2. Description of the Prior Art
Scroll type fluid displacement apparatuses are well known in the prior art. For example, Japanese Patent publication JP-A-SHO 55-35151 discloses a fluid displacement apparatus which includes a pair of interfitting scroll members. Each scroll member has a circular end plate and a spiral element extends from one end surface of the end plate. These scroll members are maintained angularly and radially offset so that both spiral elements interfit and make a plurality of line contacts between their spiral curved surfaces, to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the scroll members shifts the line contacts along the spiral curved surfaces and, as a result, the volume of the fluid pockets changes. Since the volume of the fluid pockets increases or decreases according to the direction of the orbital motion, the scroll type displacement apparatus is applicable to compress, expand or pump fluids.
In such a scroll type fluid displacement apparatus, it is desired to maintain a high degree of sealing in the axial direction between the pair of scroll members in order to more completely seal off and define the fluid pockets.
For example, JP-B-SHO 58-23516 discloses a scroll type compressor which includes a pair of scroll members. The axial end surface of one of the scroll members, which slides on the surface of the other scroll member, is coated by a coating material, and an assembly of a spring plate and an elastomeric member urging the spring plate is provided on the other scroll member. However, such a sealing mechanism is complicated in processing and expensive.
Further, Japanese Utility Model publication SHO 56-147386 discloses a scroll type compressor wherein a seal plate is disposed on the end plate of at least one of a pair of scroll members so that the seal plate covers the portion of the end plate between the walls of the spiral element extending from the end plate. The seal plate is substantially fixed between the end plate of one of the scroll members and the axial end surface of the spiral element of the other scroll member. In such an apparatus, in order to ensure that the compressor operates with an acceptable efficiency, the heights of the walls of the spiral elements must be controlled with a high degree of accuracy in production, and the thickness of the gaps maintained between the axial end surfaces of the respective spiral elements and the end plates of the respective opposed scroll members must be controlled with a high degree of accuracy during assembly. Specifically, after the compressor is assembled, the thickness of the gap which is to be maintained between the axial end surface of the spiral element of the end plate on which a seal plate is disposed, and the end plate of the other scroll, must be within a specified range in order for the compressor to achieve an acceptable level of efficiency. Thus, the difficulty of assembly and cost of production are great.
Furthermore, Japanese Utility Model publication SHO 58-8783 discloses a scroll type compressor having a sealing mechanism wherein a groove is defined on the axial end surface of a spiral element in the direction of its spiral extension, and a seal member (chip seal) having a thickness substantially greater than the depth of the groove is inserted into the groove. In such a sealing mechanism, however, fluid leaks in the direction of the spiral extension of the spiral element occur, and therefore, the capacity of the compressor is not stable. Moreover, this sealing mechanism is expensive in cost.